Edx detector

The samples were examined in the high contrast mode on a Hitachi High-Tech HT7700 transmission electron microscope (Hitachi High-Technologies Corporation, Tokyo, Japan) at 120 kV accelerating voltage. The instrument is equipped with a Bruker EDX detector that allows elemental analysis and a SAED aperture that could be used to collect diffraction patterns directly during the sample inspection. A drop of each colloidal AgNPs solution was placed on a 300-mesh carbon-coated copper grid (Ted Pella) and vacuum-dried at room temperature for 24 h prior to examination.

The sediment samples collected from sabkhas, and mangrove forest had been analyzed initially to ensure the existence of high magnesium carbonate as a bulk in these sites. One g from each sediment sample was manually grounded and homogenized with a mortar and pestle, mixed evenly, and left to dry at 37 °C overnight. The dried samples were analyzed by XRD and SEM/EDS.
The minerals formed in pure bacterial cultures were extracted from the solid media. The bacterial biomass was stripped from the surface of the solid medium by slightly scraping the top layer with a sterile scalpel. The mineral crystals were washed three times with 15 mL distilled water. This process does not alter the shape of the crystals, as confirmed by optical microscopy before and after recovery [10] . The overnight dried samples at 37 °C, were analyzed by SEM/EDS and XRD techniques.
The SEM analysis was conducted utilizing a Nova Nano Scanning Electron Microscopy equipped with a Bruker EDX Detector with a magnification of 200,000X and a resolution of 5 nm. The EDS was obtained in accordance with the “ASTM standard method E1508–12a”, using a spot size of 5 and an accelerating voltage of 20 kV with an error rate of 4%. The PANalytical- multipurpose Empyrean X-ray diffractometer was used to determine the bulk mineralogical composition of the retrieved minerals.